The invention concerns a process for the production of a titanium tetrachloride, which is nearly free from aluminum chloride, from titaniferous raw materials containing aluminum compounds by chlorinating a fine-sized titaniferous raw material in a fluid bed with the addition of a reducing agent, in which process the aluminum chloride formed in chlorination is bound with sodium chloride in a complex to be separated from the titanium tetrachloride in the form of this complex.
The base materials used for the production of titanium tetrachloride are titaniferous ores like rutile and ilmenite or other substances rich in titanium produced from such ores by enrichment of their titanium content, as e.g. in slags and concentrates. This base material is hereinafter referred to as "titaniferous raw material". The titaniferous raw materials contain compounds of other metals, e.g. aluminum. Among them there are titaniferous raw materials which contain substantial quantities of aluminum, e.g. 1 to 2% calculated as Al.sub.2 O.sub.3. On chlorination, these metal compounds are converted into their corresponding chlorides, which leave the chlorinator together with the titanium tetrachloride generated. These chlorides are then either collected by condensation together with at least part of the titanium tetrachloride, or the chlorides of lower volatility are removed in a first step before, in a second step, the crude titanium tetrachloride substantially freed from these chlorides of lower volatility is liquefied together with other chlorides of higher volatility.
"Chlorides of lower volatility" are here and further below understood to mean those metal chlorides whose boiling or sublimination point is higher than the boiling point of titanium tetrachloride under comparable pressure conditions, whereas "chlorides of higher volatility" are to mean those metal chlorides whose boiling point or point of sublimination is lower than the boiling point of titanium tetrachloride under comparable pressure conditions.
No problems are generally incurred when separating the chlorides of iron and zirconium from the titanium tetrachloride because their vapor pressure is relatively low, whereas the presence of aluminum chloride in titanium tetrachloride will cause difficulties if its quantity exceeds the quantity soluble in the titanium tetrachloride.
Owing to its relatively high vapor pressure, the aluminum chloride is carried along with the titanium tetrachloride at considerable quantities and separates from the vaporous and liquid titanium tetrachloride in a solid form as the titanium tetrachloride vapor is cooled, condensed and cooled further down, as soon as its solubility in titanium tetrachloride is exceeded. Since this solubility is considerably influenced by the prevailing termperature, aluminum chloride deposition will occur in all temperature ranges and the deposits coat the heat exchange surfaces of the cooling and condensing equipment, thus interfering with heat removal or plugging the pipelines. The aluminum chloride in the crude liquid titanium tetrachloride, moreover, has a highly corrosive effect on the customarily used metal surfaces of the equipment.